Spatial and Temporal Patterns of Southern Ocean Ventilation.

Ocean ventilation translates atmospheric forcing into the ocean interior. The Southern Ocean is an important ventilation site for heat and carbon and is likely to influence the outcome of anthropogenic climate change. We conduct an extensive backwards‐in‐time trajectory experiment to identify spatial and temporal patterns of ventilation. Temporally, almost all ventilation occurs between August and November. Spatially, "hotspots" of ventilation account for 60% of open‐ocean ventilation on a 30 years timescale; the remaining 40% ventilates in a circumpolar pattern. The densest waters ventilate on the Antarctic shelf, primarily near the Antarctic Peninsula (40%) and the west Ross sea (20%); the remaining 40% is distributed across East Antarctica. Shelf‐ventilated waters experience significant densification outside of the mixed layer. Plain Language Summary: Only a small fraction of the ocean is interacting with the atmosphere at any given time. This water is definitively found in the upper mixing layer of the ocean. When this water leaves the mixing layer and enters the ocean interior, it has "ventilated" (this term arising from the abundance of oxygen in newly ventilated water). The Southern Ocean is an important region for ventilation, and the uptake of heat and carbon dioxide there is likely to influence the limits and timescales of climate change. By calculating the 30 year history of over 480 million fluid parcels, we find that 60% of open‐ocean ventilation occurs in certain "hotspots" and almost exclusively between August and November. Key Points: Extensive backwards‐in‐time trajectories are used to explore the 30 year history of ventilation in a simulated Southern OceanLocal hotspots only account for a fraction of Southern Ocean ventilation (60%), the remaining ventilation occurs in a circumpolar patternAlmost all Southern Ocean ventilation occurs between August and November while the mixed layer is shoaling [ABSTRACT FROM AUTHOR]